The following discussion of the prior art is intended to present the invention in an appropriate technical context and allow its significance to be properly appreciated. Unless clearly indicated to the contrary, however, reference to any prior art in this specification should not be construed as an admission that such art is widely known or forms part of common general knowledge in the field.
There are various known radial engines. A radial engine generally has a crankshaft and pistons disposed in a radial relationship about the crankshaft. The pistons are disposed to engage the crankshaft such that there is correspondence between the rotation of the crankshaft and the reciprocating motion of the pistons in their cylinders.
In one known radial engine, the crankshaft is substituted by a crank that is configured to permit the pistons to be aligned with one another along the length of the rotational axis of the crank. As the pistons are aligned, the normal stepped-waveform crankshaft configuration cannot be used. Usually this is substituted by a cam-and-follower arrangement to permit a translation between the linear reciprocating motion of the pistons and the rotational motion of the crank. It will be appreciated that, due to the alignment of the pistons, this arrangement provides a significantly greater degree of compactness than in the case of engines where the pistons are positioned at spaced intervals along the length of the crankshaft.
However, due to the usual cam-and-follower arrangements, such radial engines have disadvantages relating to the reaction forces exerted by the cranks on the pistons, via the followers and connecting rods. Further disadvantages relate to the methods adopted for effecting suitable engagement between the followers and the cranks. For example, certain of these engines have required cranks with particularly complex structures and complex means for providing lateral support to the connecting rods. Such structures are expensive and difficult to produce and hence are often not suitable for large-scale production.